Project Summary/Abstract Estrogen level decreases in post-menopausal women have been shown to increase the risk of memory loss and Alzheimer?s disease. While these effects might be mitigated using hormone replacement therapy, traditional estrogen-based hormone therapies also lead to increased risk of cancer, heart disease and stroke. These adverse effects are mediated predominantly by estrogen receptor-alpha (ER?). Relevant to menopause, aging significantly reduces levels of ER??and ER??in the hippocampus, suggesting an association with age-related memory decline; but, ER??remains the predominant isoform. We hypothesize that an optimal treatment for age-related memory decline in post-menopausal women may be via treatment that selectively activates hippocampal ER?. Our long-term goal is to develop safer and more selective ER? agonists as therapeutics for treating dementia in post-menopausal women. Our objective is to optimize and characterize a novel class of molecules comprised of a 4-hydroxymethyl- cyclohexane ring tethered to a phenol ring, making it an A-C estrogen that closely resembles the naturally occurring estrogen molecule, but lacking the B and D rings. The rationale for the proposed research is that it will provide essential foundational knowledge about estrogenic regulation of cognition that will advance the development of novel treatments; and, it will provide mechanistic insights into the remarkable ER? selectivity that can be achieved with simplified versions of the estrogen itself. Our Aims Are to: ? Aim 1. Characterize and optimize the structural features of ISP358-2 that are responsible for its high ER? selectivity. We will use docking to guide design and optimization of ISP358-2 based on activity in cell-based (ER? vs. ER? agonist activity) assays, and then demonstrate in vivo efficacy for memory consolidation. ? Aim 2. Determine mechanism of ISP538-2 ER? agonist selectivity. We will measure and characterize ability of optimized ISP358-2 and control (PPT, E2) compounds to cause agonist conformational changes needed to recruit brain-relevant coactivator, thereby inducing transcription. ? Aim 3. Establish the therapeutic potential of the optimized ISP358-2 lead molecule by determining the neural mechanism through which it enhances memory consolidation. We will use intracranial infusions to measure the extent to which ISP358-2 acts like an ER agonist to trigger rapid cell signaling, alter hippocampal morphology, and enhance memory.